/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/************************************************************************
 * kernel/pthread/pthread_completejoin.c
 *
 *   Copyright (C) 2007, 2009, 2011, 2013 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ************************************************************************/

/************************************************************************
 * Included Files
 ************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <stdbool.h>
#include <pthread.h>
#include <errno.h>
#include <debug.h>

#include "sched/sched.h"
#include "group/group.h"
#include "pthread/pthread.h"

/************************************************************************
 * Pre-processor Definitions
 ************************************************************************/

/************************************************************************
 * Private Type Declarations
 ************************************************************************/

/************************************************************************
 * Global Variables
 ************************************************************************/

/************************************************************************
 * Private Variables
 ************************************************************************/

/************************************************************************
 * Private Functions
 ************************************************************************/

/************************************************************************
 * Name: pthread_notifywaiters
 *
 * Description:
 *   Notify all other threads waiting in phread join for this thread's
 *   exit data.  This must  be done by the child at child thread
 *   destruction time.
 *
 ************************************************************************/

static bool pthread_notifywaiters(FAR struct join_s *pjoin)
{
	int ntasks_waiting;
	int status;

	svdbg("pjoin=0x%p\n", pjoin);

	/* Are any tasks waiting for our exit value? */

	status = sem_getvalue(&pjoin->exit_sem, &ntasks_waiting);
	if (status == OK && ntasks_waiting < 0) {
		/* Set the data semaphore so that this thread will be
		 * awakened when all waiting tasks receive the data
		 */

		(void)sem_init(&pjoin->data_sem, 0, (ntasks_waiting + 1));

		/* Post the semaphore to restart each thread that is waiting
		 * on the semaphore
		 */

		do {
			status = pthread_sem_give(&pjoin->exit_sem);
			if (status == OK) {
				status = sem_getvalue(&pjoin->exit_sem, &ntasks_waiting);
			}
		} while (ntasks_waiting < 0 && status == OK);

		/* Now wait for all these restarted tasks to obtain the return
		 * value.
		 */

		(void)pthread_sem_take(&pjoin->data_sem, false);
		return true;
	}

	return false;
}

/************************************************************************
 * Name: pthread_removejoininfo
 *
 * Description:
 *   Remove a join structure from the local data set.
 *
 * Parameters:
 *   pid
 *
 * Return Value:
 *   None.
 *
 * Assumptions:
 *   The caller has provided protection from re-entrancy.
 *
 ************************************************************************/

static void pthread_removejoininfo(FAR struct task_group_s *group, pid_t pid)
{
	FAR struct join_s *prev;
	FAR struct join_s *join;

	/* Find the entry with the matching pid */

	for (prev = NULL, join = group->tg_joinhead; (join && (pid_t)join->thread != pid); prev = join, join = join->next) ;

	/* Remove it from the data set. */

	/* First check if this is the entry at the head of the list. */

	if (join) {
		if (!prev) {
			/* Check if this is the only entry in the list */

			if (!join->next) {
				group->tg_joinhead = NULL;
				group->tg_jointail = NULL;
			}

			/* Otherwise, remove it from the head of the list */

			else {
				group->tg_joinhead = join->next;
			}
		}

		/* It is not at the head of the list, check if it is at the tail. */

		else if (!join->next) {
			group->tg_jointail = prev;
			prev->next = NULL;
		}

		/* No, remove it from the middle of the list. */

		else {
			prev->next = join->next;
		}
	}
}

/************************************************************************
 * Public Functions
 ************************************************************************/

/************************************************************************
 * Name: pthread_completejoin
 *
 * Description:
 *   A thread has been terminated -- either by returning, calling
 *   pthread_exit(), or through pthread_cancel().  In any event, we must
 *   complete any pending join events.
 *
 * Parameters:
 *   exit_value
 *
 * Returned Value:
 *   OK unless there is no join information associated with the pid.
 *   This could happen, for example, if a task started with task_create()
 *   calls pthread_exit().
 *
 * Assumptions:
 *
 ************************************************************************/

int pthread_completejoin(pid_t pid, FAR void *exit_value)
{
	FAR struct task_group_s *group = task_getgroup(pid);
	FAR struct join_s *pjoin;

	svdbg("pid=%d exit_value=%p group=%p\n", pid, exit_value, group);
	DEBUGASSERT(group);

	/* First, find thread's structure in the private data set. */

	(void)pthread_sem_take(&group->tg_joinsem, false);
	pjoin = pthread_findjoininfo(group, pid);
	if (!pjoin) {
		sdbg("Could not find join info, pid=%d\n", pid);
		(void)pthread_sem_give(&group->tg_joinsem);
		return ERROR;
	} else {
		bool waiters;

		/* Save the return exit value in the thread structure. */

		pjoin->terminated = true;
		pjoin->exit_value = exit_value;

		/* Notify waiters of the availability of the exit value */

		waiters = pthread_notifywaiters(pjoin);

		/* If there are no waiters and if the thread is marked as detached.
		 * then discard the join information now.  Otherwise, the pthread
		 * join logic will call pthread_destroyjoin() when all of the threads
		 * have sampled the exit value.
		 */

		if (!waiters && pjoin->detached) {
			pthread_destroyjoin(group, pjoin);
		}

		/* Giving the following semaphore will allow the waiters
		 * to call pthread_destroyjoin.
		 */

		(void)pthread_sem_give(&group->tg_joinsem);
	}

	return OK;
}

/************************************************************************
 * Name: pthread_destroyjoin
 *
 * Description:
 *   This is called from pthread_completejoin if the join info was
 *   detached or from pthread_join when the last waiting thread has
 *   received the thread exit info.
 *
 *   Or it may never be called if the join info was never detached or if
 *   no thread ever calls pthread_join.  In case, there is a memory leak!
 *
 * Assumptions:
 *   The caller holds tg_joinsem
 *
 ************************************************************************/

void pthread_destroyjoin(FAR struct task_group_s *group, FAR struct join_s *pjoin)
{
	svdbg("pjoin=0x%p\n", pjoin);

	/* Remove the join info from the set of joins */

	pthread_removejoininfo(group, (pid_t)pjoin->thread);

	/* Destroy its semaphores */

	(void)sem_destroy(&pjoin->data_sem);
	(void)sem_destroy(&pjoin->exit_sem);

	/* And deallocate the pjoin structure */

	sched_kfree(pjoin);
}
